Chromecast Audio compatible speakers and cables

Chromecast Audio works right out-of-the-box with your existing speaker systems that have an aux input or line input. Chromecast Audio also works on systems with RCA inputs and optical digital inputs. Note: RCA and optical cables are not included with your Chromecast Audio.

This provided 3.5mm cable supports a stereo analog audio signal, and is designed to plug into input ports labeled things like "AUX IN", "LINE-IN" or some symbolic icon representing the same. 3.5mm stereo inputs are commonly found on desktop computer speakers, media player docking speakers, and compact portable speakers.

3.5mm-to-RCA cable - Not included with Chromecast Audio

This cable is a commonly available retrofit cable that converts the stereo analog output from Chromecast Audio into a stereo RCA connection.
RCA inputs are common on many people's favorite stereo setups they've owned for years, and sometimes decades, like AV receivers, mini/micro bookshelf systems, and studio monitor speakers.

Mini-TOSLINK-to-TOSLINK (optical) cable - Not included with Chromecast Audio

This cable is another commonly available adapter that provides access to the optical digital audio output on Chromecast Audio. Digital audio is popular among users with high power speaker systems.
TOSLINK inputs are commonly found on modern AV receivers, soundbars, and some high-end desktop speakers, and studio monitor speakers.

Chromecast Audio works with "active speakers" where power amplifiers are integrated as part of the speaker. Common active speaker systems are Bluetooth speakers, soundbars, docking speakers, portable speakers, desktop computer speakers, studio monitors, etc.

Chromecast Audio can also drive "passive speakers", however there must be an amplifier in between Chromecast Audio and the "passive speakers", which do not have amplifiers built into them. Amplifiers exist in Stereo receivers, AV receivers, mini/micro bookshelf units, and as standalone amplifiers for higher-end Hi-Fi component systems.

Chromecast Audio provides relatively low-power, or line-level audio signals to a speaker system. This signal is common for connection between audio systems, but is not in itself powerful enough to drive high enough audio listening levels for home listening. For this, Chromecast Audio depends on a power amplifier to amplify the signal to home audio listening levels